Expand.
Explanation: $\begin{aligned} &\phantom{=}({y^2+6})(-2y^2+7) \\\\ &={y^2}(-2y^2+7){+6}(-2y^2+7) \end{aligned}$ $\begin{aligned} &=-2y^4+7y^2-12y^2+42 \\\\ &=-2y^4-5y^2+42 \end{aligned}$